1. Field of the Invention
This invention relates to a method of preparing oil-soluble Mannich condensation products from oxidized olefin polymers, amines and aldehydes. More particularly, it relates to a process for preparing oil-soluble Mannich condensation products wherein the amine is prereacted with a sulfonic acid or an ammonium sulfonate before contact with the oxidized olefin polymer and the aldehyde.
2. Description of the Prior Art
The operation of diesel and spark ignition internal combustion engines is typically accompanied by lubricant deterioration, which results in the formation of sludge, lacquer and resinous deposits on interior engine surfaces. These lubricant deterioration products reduce engine efficiency and accelerate engine wear. In order to prevent or reduce the formation of these deposits, a wide variety of chemical additives have been developed for incorporation into lubricating oils. These additives, which are commonly referred to as detergents or dispersants, have the ability to keep deposit-forming materials suspended in the oil so that the engine remains in a clean and efficient operating condition for extended periods of time.
Lubricating oils have a tendency to become thin at elevated temperatures while becoming thick at low temperatures. In the case of a crankcase lubricating oil, it is desirable that the oil not become so thick in a cold engine that starting is difficult. On the other hand, the oil must remain sufficiently viscous in a hot engine so that an oil film is maintained between the moving parts. As a consequence, it is frequently necessary to incorporate additives into lubricating oils which serve to improve the viscosity-temperature relationship. Additives which have the ability to reduce the variation with temperature of the viscosity of a lubricating oil are commonly referred to as viscosity index improvers.
U.S. Pat. No. 3,872,019, issued to Culbertson et al. on Mar. 18, 1982, discloses and claims lubricant additives which exhibit both dispersant and viscosity index improving properties. These additives are obtained by the Mannich condensation of an oxidized, high molecular weight, amorphous ethylene-propylene copolymer with a formaldehyde-yielding reactant and a primary or secondary amine or polyamine. This patent does not, however, either teach or suggest the use of a sulfonic acid or ammonium sulfonate in the condensation process.
U.S. Pat. No. 4,131,553, issued to West on Dec. 26, 1978, is also directed to oil-soluble Mannich condensation products which possess both dispersant and viscosity index improving properties when added to a lubricating oil. This patent discloses that such products can be prepared by reacting a high molecular weight, oxidized, amorphous addition polymer with a formaldehyde-yielding reagent and an amine in the presence of an oil-soluble sulfonic acid. However, this patent teaches that the sulfonic acid must be added during the Mannich condensation reaction of the oxidized copolymer, at the same time as, or after the addition of the amine. The patent fails to teach the prereaction of amine and sulfonic acid and fails to suggest that such a procedure would be desirable.